The accident airplane wasn't owned by the PIC. Per the Prelim, he borrowed the airplane from an acquaintance. May not have known there was a problem with it.
The fact that the airplane flew to AVX from SMO and then they couldn't get the right engine started leaves me with the impression there was more going on in the electrical system than just a weak battery (alternator/Voltage Regulator...etc).
After reading the prelim, the scenario that initially came to mind was raising the gear handle caused a catastrophic blackout. That would certainly explain the flight path and outcome.
This could be a very plausible scenario. I had the catastrophic electrical system failure about 15 years ago due to some poor airmanship in a Cessna 337. I flew it down to an avionics place to get some items fixed and ended up having an alternator replaced. The repairs had taken much longer than expected which had frustrated me. I had a self-imposed timeline to get the back to base as I was leaving town to go to work for a few weeks.
I was keen to finally pick it up, but there was a further issue. I can't remember the details but it had been discovered that there was some sort of a relay or fuse that was discovered to not be working and also needed replacing in order to get the new front alternator to be able to charge the system. I didn't really understand the problem when explained to me but decided that I was comfortable to pick it up and fly it back to home base for the final repair because I had had alternator failures in the past and had been able to safely get back home with one of them inop.
It was a beautiful day and I had two short 30 minute legs to fly and then a long leg(2 hours). According the indications, there was positive charging from one of the alternators during flight. There was no voltmeter in the aircraft.
The first two legs seemed fine. I did get a hint if an issue that was ignored for the third flight. I had trouble starting the back engine which takes more electrical power as it is further from the battery but I had seen that sort of thing before and when the front engine was revved up, I was able to crank over the rear engine and start it. A red flag appeared on the heading indicator while taxiing out but they had replaced the indicator at the avionics shop and I figured that it was a problem with the new one. In addition, there was an alternator low volts light flashing sometimes in coordination with the beacon flashing but I think it was OK when the front engine was revved up. I ignored these hints and took off on the nice sunny late afternoon. It appears that the battery was not charging even though there was an indication of a positive charge coming from the front engine.
When the gear was selected up, I had an electrical power failure right away. I remained Nordo and diverted back to the airport with the avionics shop and was able to pump down the gear and do a flapless landing. Not sure how much light would have been available on the instrument panel at night but I think that I did have a bit of electrical power left initially to retract the flaps but I could barely see the gear indicator lights to confirm they were down.
In the end, I had assumed that the battery was being charged because of the positive indication from the alternator. Obviously, this was not the case.
Of course, I made an error by taking an aircraft with an inoperative item like this on a flight. Perhaps a single leg with minimal electrical usage, such as leaving the gear down followed by electrical master off for the flight would have been plausible(I have done that before for a gear warning horn that could not be silenced).
Taking off for a flight where instrument flying is required is a bad idea when there are electrical issues. Also remember if airborne is such a situation, that not operating the landing gear(that has an electrical motor) or delaying operation could prevent an electrical failure happening while instrument flying is required. Perhaps you had an electrical issue and could wait until visual before extending the gear. Or perhaps you decide to manually extend the gear to save electrical power. If the gear retraction finally killing the electrical system theory is correct, maybe not retracting it would have been wiser on that flight out of Catalina.
